Patterns in the parasite community structure of Icelandic rock ptarmigan 2006 - 2012?
The Icelandic rock ptarmigan Lagopus muta population cycles with peak numbers c. every 10 years. Researchers intend to better understand what drives these cycles. For this reason, a research project on the relationship between population change of ptarmigan and health related parameters was started in 2006 and is supposed to run for 12 years. As a part of this project and because parasite-host interactions have been suggested as one of the forces driving population cycles, we investigate the parasite community structure. From 2006-12 in October, each year we collected c. 100 ptarmigan in northeast Iceland and examined them for parasites and signs of disease. The parasite fauna consisted of 17 species, 10 ectoparasites and seven endoparasites. Out of 632 investigated birds, 623 harboured ectoparasites and 536 endoparasites. Averaged five (max 9) parasite species lived on each bird. All parasites were more prevalent in juvenile birds except the mite Mironovia lagopi and the nematode Capillaria caudinflata that were more prevalent in adults. Most prevalent was the mite Tetraolichus lagopi, followed by the coccidian Eimeria muta and the louse Gonoides lagopi. While the overall parasite load was about equal in juvenile male and female birds, it was higher in adult females than males. Over the seven years of this study, endo- and ectoparasite loads fluctuated conversely in synchrony, and this wave-like pattern featured particularly in juvenile birds. This observation regarding the juvenile birds is of importance for future exploration as changes in a mortality rate specific to them (“juvenile excess mortality”) drive the ptarmigan cycle in a demographic sense.